This invention relates to exercise devices and, more particularly, to an isokinetic exercise apparatus for exercising the legs and lower body.
Numerous types of devices have been developed for exercising various muscles or muscle groups. Exercise devices generally provide some sort of resistance to the user""s movement. For example, the resistance may be provided by weights, elastic elements such as springs, or pneumatic or hydraulic devices. Exercise machines which use weights to provide resistance are commonly bulky and not easily portable. Elastic elements generally provided resistance which varies as the elastic element is deformed. Also, elastic elements can wear out over extended use. Pneumatic and hydraulic resistance devices can provide a resistance which varies in proportion to the force applied by the user. Exercise in which the resistance is proportional to the force applied by the user is referred to as xe2x80x9cisokineticxe2x80x9d exercise. Prior isokinetic exerciser devices for exercising the legs and lower body were free standing bulky devices which were not readily portable.
It is an object of the invention to provide an easily portable and lightweight isokinetic exercise apparatus for exercising the legs and lower body.
The exercise apparatus according to invention includes a substantially rigid base and an isokinetic resistance unit mounted thereon. The isokinetic resistance unit is connected to the base by a pivot connection which allows the resistance unit to pivot about an axis parallel to a base axis. The base has two support areas spaced apart along the base axis, one support area on each side of the point at which the resistance unit is connected to the base. The apparatus further includes a harness or belt which is connected to an upper end of the resistance unit.
The isokinetic resistance unit relies upon a fluid, preferably air, for providing resistance. Also, the preferred resistance unit utilizes a negative pressure to provide resistance rather than a positive pressure. By utilizing negative pressure, the resistance unit according to the invention simplifies the required sealing arrangements.
The preferred resistance unit comprises a cylinder with a piston slidably received therein. A rod is connected to the piston and extends generally parallel and coaxially with the cylinder. The rod and piston are adapted to move with respect to the cylinder between a retracted position and an extended position. In the retracted position, the piston resides near a sealed lower end of the cylinder and the rod extends a relatively short distance beyond the opposite end of the cylinder. However, when the piston slides to the extended position in an upper end of the cylinder, the rod extends substantially beyond the upper end of the cylinder. The area of the cylinder defined between the piston and lower end of the cylinder forms a working chamber. The resistance unit also includes an air flow resistance opening and a one-way valve associated with the working chamber. A return spring may act between the piston and cylinder to bias the piston toward the lower end of the cylinder.
In operation, the user stands on the base and pulls the rod and piston to the extended position to allow the belt to be connected around the user""s waist. With the belt fixed around the user""s waist, the user bends their legs while keeping their back substantially perpendicular to the base and floor, and then completes the repetition by straightening their legs to return to the starting position. The rod and piston in the resistance unit move toward the retracted position as the user bends their legs, and then move toward the extended position as the user straightens their legs. However, the isokinetic resistance unit resists the movement toward the extended position, applying a resisting force through the rod and belt positioned around the user""s waist. The resistance is generated by the negative pressure produced in the working chamber portion of the cylinder as the piston moves toward the extended position. The air flow resistance opening limits air flow into the working chamber, preventing the pressure in the working chamber from quickly equalizing with ambient pressure and maintaining the negative working chamber pressure as the user pulls the piston and rod toward the extended position.
The apparatus according to the invention provides good exercise for the lower body and particularly the legs. Yet the device is lightweight, easily portable, and may be stored easily. The use of negative pressure in the working chamber to provide resistance also simplifies the sealing arrangement required in the device. In particular, a sliding seal is required only between the piston and the cylinder.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.